One of the Most Efficient Engines Built So Far Has $1900 ^ { \circ } \mathrm { C }$

One of the most efficient engines built so far has the following characteristics: The combustion chamber temperature is $1900 ^ { \circ } \mathrm { C }$ , the exhaust temperature $= 430 ^ { \circ } \mathrm { C } , 7.0 \times 10 ^ { 9 }$ cal of fuel produces $1.4 \times 1010 \mathrm {~J}$ of work in one hour. ( $1 \mathrm { cal } = 4.186 \mathrm {~J}$ )
(a) What is the actual efficiency of this engine?
(b) What is the power output of this engine?
(c) What would be the maximum possible efficiency for an engine using the same temperature extremes?